Upon completing Career mode, use Samson as your wingman with Neville in your crew. You can repeat all the races where you used a wingman, and using a wingman net's you an extra $250. You can gain the bonus on first time races as well.

Maximizing Speedtrap advantage

Before Speedtrap races, activate your Blocker/Brawler. When coming up on a speed trap, stop your B/B. It will crash the other cars, and dramatically slow their time. The best time to use it is right before the Trap.